1. Field of the Invention
Embodiments of the current invention relate to printing devices and toner cartridges.
2. Description of the Related Art
Printing devices, such as copiers, printers, fax machines, multi-function machines, and the like, typically utilize a toner cartridge to supply the pigment that forms printed text and images on a paper printout. The toner is a dry powder mix that resides in a chamber within the cartridge. In order to alert users to replace the toner cartridge, it is beneficial for the printing device to track the volume or quantity level of toner in the toner cartridge. However, the printing device cannot always detect the level of toner in the toner cartridge. In those cases, it typically can detect how much toner is being used during the print process so that it will have accurate readings for the entire life cycle of the cartridge. The toner cartridge itself may include a sensor system that is able to detect the level of the toner in the cartridge, but only after the level of the toner is below a certain value, such as around 10%. Therefore, the printing device is able to report the level of toner volume in the toner cartridge by estimating the level of toner based on the usage of toner during printing until a predetermined level (controlled by the sensor system) is reached, such as 10%. At this point, the printing device no longer estimates, but relies on the actual level of toner as reported by the toner cartridge. This process provides an accurate reporting of the level of toner by assuming a certain initial volume of toner in the toner cartridge. The initial volume is specified by an original equipment manufacturer (OEM) and is typically the same volume as is included in the original toner cartridge. FIG. 1 shows a plot of toner usage for an original cartridge with an exemplary initial volume that is capable of printing approximately 15,000 pages.
When the toner in the original toner cartridge runs out, a replacement toner cartridge must be installed in the printing device. Often, the replacement toner cartridge is supplied from a third party and may include a greater or smaller initial volume of toner than was in the original cartridge. The printing device may assume that the replacement toner cartridge includes the same volume of toner as was in the original cartridge. This will lead to erroneous reporting of the level of toner in the toner cartridge. FIG. 2 shows a plot of toner usage for an exemplary replacement toner cartridge with a volume capable of printing approximately 19,000 pages. The printing device assumes that the initial volume of the toner cartridge is capable of printing approximately 15,000 pages. FIG. 2 also shows a dashed line indicating the expected usage of toner for the cartridge. The plot shows the level of toner L3 as reported by the printing device. The printing device estimates the level of toner L3 based on usage of the printer until the level of toner L3 is approximately 11%, seen as the diagonal portion of the level of toner L3 from 100% to approximately 11%. At this point, the printing device relies on the toner cartridge to report the level of toner L3. However, because the toner cartridge had a greater initial volume of toner than estimated by the printing device, there is a greater level of toner L3 in the cartridge than the toner cartridge can detect—perhaps 25%-30%, instead of 11%. As a result, the printing device continues to report the level of toner L3 as being 11% until the level of toner L3 is low enough for the toner cartridge to detect. This is seen as a flat, horizontal portion of the level of toner L3 on the plot. Once the level of toner L3 is low enough for the toner cartridge sensor system to detect, the printing device accurately reports the level of toner L3 until the toner is depleted at approximately 19,000 pages, shown as the diagonal portion of the level of toner L3 from approximately 11% to 0%.
The erroneous reporting by the printing device of the level of toner in the toner cartridge can lead to ordering of toner cartridges that are not necessary, especially if usage projections are based on the initial usage of toner. The erroneous reporting may also lead to replacement of toner cartridges that are not yet empty, or possibly to unnecessary service calls.